His assailant stabbed the 50-year-old repeatedly in front of dozens of stunned shoppers.

A 30-year-old man was arrested a short time later in nearby Twaddell Avenue.

A member of Tesco’s staff rang emergency services and the injured man was rushed to the Royal Victoria Hospital.

Police said he suffered multiple stab wounds and was in a serious condition last night after undergoing surgery.

There was speculation that a possible motive for the stabbing was revenge for the murder of Bobby Moffett in May last year.

The 43-year-old was gunned down in broad daylight on the Shankill Road in Belfast.

The Independent Monitoring Commission reported that his murder had been sanctioned at UVF leadership level.

Mr Stockman is a close associate of the UVF leader John ‘Bunter’ Graham and is a senior loyalist figure in the Shankill Road area.

Security journalist Brian Rowan said: “Stockman is one of the most senior and influential leaders in the UVF organisation.

“He is leader of what that organisation calls its 1st Battalion on the Shankill Road.

“He has been influential in the big decisions of that organisation in recent years, including its May 2007 ‘endgame’ statement when it talked about assuming a civilianised role, and then the decommissioning move in 2009 when, off-camera at a news conference, he read the UVF statement.”

Police said inquiries were ongoing and that they could neither comment on the motive for the attack nor on any UVF involvement.

The supermarket, which is normally open until midnight, was closed after the incident as police examined the scene.

Rush hour traffic leaving the city along the nearby Shankill and Crumlin Roads also ground to a halt as police examined the scene.